Returns a list of results of applying the given transform function to
an each char sequence representing a view over the window of the given size
sliding along this char sequence with the given step.

Note that the char sequence passed to the transform function is ephemeral and is valid only inside that function.
You should not store it or allow it to escape in some way, unless you made a snapshot of it.
Several last char sequences may have less characters than the given size.

Both size and step must be positive and can be greater than the number of elements in this char sequence.